1. Technical Field
The invention generally relates to a light-emitting device, a planar light source and a direct type backlight module.
2. Discussion of Related Art
Nowadays, liquid crystal materials are widely utilized in various liquid crystal displays (LCDs) having different sizes for different applications, such as TVs, liquid crystal projectors, mobile telephones, personal digital assistants (PDAs), etc. Since liquid crystal itself cannot emit light, light sources must be utilized to irradiate/illuminate liquid crystal for image display. The light sources are called backlight sources because they are usually configured behind liquid crystal panels. A combination of all components behind the liquid crystal panels, including the light sources, is generally referred to as a backlight module. Usually, backlight modules can be classified into edge type backlight modules and direct type backlight modules.
Edge type backlight modules are usually utilized in middle sized or small sized LCDs, such as LCDs used in mobile telephones. Direct type backlight modules are usually utilized in large sized LCDs, such as LCDs used in TVs. In direct type backlight modules, a plurality of cold cathode fluorescent lamps (CCFLs) are generally used as light sources. The plurality of CCFLs are linear and arranged parallel to each other. Due to the spacing between the LCDs, the resulting light source is discontinuous. The CCFLs may also have differences in brightness and chroma between each other such that the illumination of the direct type backlight module is poor. As well as this, the CCFLs contain mercury, making them difficult and dangerous to dispose of safely.
What is needed, therefore, is a light-emitting device, a planar light source and a direct type backlight module with uniform brightness and chroma.